A polymer electrolyte fuel cell is a fuel cell in which a solid polymer electrolyte is sandwiched by an anode and a cathode with the anode being supplied with a fuel and the cathode being supplied with oxygen or air and thereby oxygen is reduced at the cathode to produce electricity.
An electrode catalyst of the fuel cell has conventionally been platinum, and yet, to decrease use amount of the expensive platinum, its alternative, an alloy of platinum and other metal element(s), has been focused. There is a problem, however, with the other metal element(s):lower catalyst activity and durability than platinum (their elution during the operation of fuel cells).
To solve that problem, Non-Patent Literature 1 discloses a method for potential scanning (potential cycling) of platinum-palladium alloy catalysts. This method is described to be able to improve activity and durability of the platinum-palladium alloy catalysts.
Patent Literature 1 describes bringing platinum-palladium-containing catalyst particles into contact with an acid solution thereby dissolving the easily soluble palladium and causing platinum to precipitate on (111) surface of palladium appearing on their outmost surfaces in order to obtain catalyst particles with high durability (less elution of platinum).